Infrared band pass system for optical detection of parameters

Abstract

A glass substrate having an average thickness of the glass substrate from 0.01 to 1.2 mm and having a temperature dependence of refractive index at a wave-length of 850 nm in a temperature range from −40° C. to 60° C. of not more than 10×10−6/K.

What is claimed is: 
     
       1. A glass substrate having an average thickness of the glass substrate from 0.01 to 1.2 mm and having a temperature dependence of refractive index at a wave-length of 850 nm in a temperature range from −40° C. to 60° C. of not more than 10×10 −6 /K. 
     
     
       2. The glass substrate according to  claim 1 , wherein the glass substrate has a transmission of more than 90% at a 10 mm thickness in a wavelength region of 780 to 1,000 nm. 
     
     
       3. The glass substrate according to  claim 1 , wherein the glass substrate has a Knoop hardness HK0.1/20 of more than 450. 
     
     
       4. The glass substrate according to  claim 1 , wherein an average thickness of the glass substrate is 0.1 to 0.7 mm. 
     
     
       5. The glass substrate according to  claim 1 , wherein the glass substrate is produced by a drawing process. 
     
     
       6. The glass substrate according to  claim 1 , wherein the glass substrate is produced by a float process. 
     
     
       7. An infrared band pass filter, comprising:
 a glass substrate; and 
 at least one coating applied to the glass substrate, the glass substrate having a thickness of 0.01 to 2 mm, the glass substrate having a temperature dependence of refractive index at a wavelength of 850 nm in a temperature range from −40° C. to 60° C. of not more than 10×10 −6 /K, and the at least one coating having a thickness of not more than 0.5 mm. 
 
     
     
       8. The infrared band pass filter according to  claim 7 , wherein the band pass filter has a passband in a wavelength region of from 780 nm to 1,000 nm. 
     
     
       9. The infrared band pass filter according to  claim 8 , wherein the band pass filter has a passband in a wavelength region of from 800 nm to 900 nm. 
     
     
       10. The infrared band pass filter according to  claim 7 , wherein a temperature dependence of refractive index of the at least one coating is less than 0.001/K. 
     
     
       11. The infrared band pass filter according to  claim 7 , wherein a ratio of the temperature dependence of refractive index of the coating to the temperature dependence of refractive index of the glass substrate does not exceed 1,000. 
     
     
       12. The infrared band pass filter according to  claim 7 , wherein the coating has from 10 to 1,000 layers. 
     
     
       13. The infrared band pass filter according to  claim 7 , wherein the at least one coating is formed by physical vapor deposition. 
     
     
       14. The infrared band pass filter according to  claim 7 , wherein the at least one coating is formed by a sol-gel process. 
     
     
       15. The infrared band pass filter according to  claim 7 , wherein coating materials are selected from Nb 2 O 5 , TiO 2 , Ta 2 O 5 , SiO 2 , MgF 2 , Al 2 O 3 , HfO 2  and ZnO 2 . 
     
     
       16. An infrared band pass filter, comprising:
 a glass substrate; and 
 at least one coating formed on the glass substrate, the glass substrate having a thickness of 0.01 to 2 mm, the at least one coating having a thickness of not more than 0.5 mm, and a temperature dependent center wavelength drift in the filter is less than 15 nm in a temperature range from −40° C. to 60° C.